Fire fighters in Guangxi Zhuang autonomous region said Saturday that they have spayed tonnes of purifying solution into a river found to be contaminated with the heavy metal cadmium on Thursday.

Fire engines have been used to spread 80 tonnes of neutralizers, which were made from dissolved aluminum chloride, into the Longjiang River, said an official with the fire brigade of Hechi city.

Excessive cadimum levels were detected in the Hechi section of the Longjiang River, on Thursday, killing fish and prompting concerns over drinking water.

The cadimum amount at the Luodong Hydropower Station at the river's lower reaches was 0.0247 milligrams per liter, three times higher than the official limit, according to the city's environment authorities.

Local residents have been advised not to drink water from the river, and local authorities are still searching for the source of the pollution.

Cadimum, a chemical that is mostly found in industrial effluents, is carcinogen.